I seldom went out for dinner due to the location of school and the lack of money when I was in NCTU. But since I have came to Taipei, I started to have opportunities to dine together with others. Once I went with a lot of people, when it comes to paying, everyone put her money on the table. But the person who collected the money and payed for us later found out the money was not enough. However, nobody was sure who was responsible for that. I also have lost 200-300 dollar once when I went out with others.
Indeed, if we are unable to pay individually, it's often risky to dine together. There are four problems that might arise: (1) some people might pay less than required (2) there might may fake money (3) the restaurant could also make mistakes with the amount of money (4) some friends might quickly take away his money when the store gives you your change, making it hard to confirm the amount.
Even though it might be possible to prepare the change beforehand so I can also pay the exact amount for myself, it's still easy to forget about it. So I start to wonder whether there could be a payment system that could solve all the problems.
It basically works as follows. After dining, we could create a dining event with this app and add everybody. Each person could enter his amount and the system would check has balance and pay the amount to the friend who are going to pay physically. The system also displays the total amount so you could check the change from the store easily.
You could also take a picture with the your receipt so you could check who does not pay enough when you later find out the money is not enough.
Because all the communication happens on the platform, all friends could see your dispute, making it easy to pressure the one responsible to pay back.
If he really does not want to correct the amount, you could give him a bad review, so when he go out with others next time, everyone could be aware of this.
Of course, if the system could just pay to the restaurant, then all of this is not required.
This payment system may utilize peer pressure to promote their apps, so they can make everyone uses the system and make money.